Generally, when the needle or catheter penetrates the skin for access to an artery, a vein, or a fistula as in hemodialysis, there is a certain amount of bleeding that takes place when it is removed. In blood donation, for example, when the donor needle is removed, the donor is asked to elevate his or her arm and to press cotton gauze against the needle penetration site for some minutes, until the wound has completely clotted.
In the field of extracorporal blood processing such as hemodialysis, larger diameter needles, such as 15 gauge needles, are used rather than the smaller needles used for blood collection and blood sampling. The blood pressure is higher due to the fistula's arterialized vein structure, and the patient is anticoagulated for the extracorporeal procedure. Thus, when the needle is withdrawn, bleeding is more pronounced, and must be dealt with more rigorously, to avoid the loss of a significant amount of blood through bleeding. Since hemodialysis in particular is performed frequently on chronic patients, even small blood losses can add up, so that it would be desirable to minimize the bleeding to avoid the relatively small amount of blood that is conventionally lost when dialysis needles are withdrawn.
Generally, compression is used for a period of time after withdrawal of any hollow bore needle, to achieve hemostasis. Typically, this is done with absorbent gauze manually pressed over the cannulation site as soon as the needle is removed. As the gauze is absorbent, this method does not staunch bleeding, but merely creates a slowing of the blood leakage so the body's natural clotting mechanisms can eventually take over and stop the blood flow. In hemodialysis, it is not uncommon to use five or six successive gauze compressions over a period of 20-30 minutes until hemostasis is achieved.
The prior art also discloses non absorbent materials to stop cannulation site bleeding. One way of accomplishing this was proposed in McRae et al. U.S. Pat. No. 4,233,980, where a pressure bladder made of flexible, non-elastic material and carried on a rigid, floor mounted arm is pressed against a site to produce hemostasis after an arterial puncture. Another way was proposed in Stanulis U.S. Pat. No. 4,182,338 where a skin contacting surface as soft as 25 Shore A durometer is part of a strap arrangement around the portion of the body where blood loss is to be prevented by compression of the skin contacting surface. Another way is Roth U.S. Pat. No. 5,263,965 which comprises a rigid disc as a manual compression aid.
Another significant problem with hollow bore needle cannulation is cannulation-induced infection to the cannulation tract and/or vessel. Although the needle is sterilized at the time of manufacture, and is maintained sterile in its package, needles may become unsterile as soon as its sterility protector is removed. At this stage it is susceptible to being contaminated by touch or air-borne bacteria. Or, the act of cannulation may drag into subcutaneous tissues bacteria from the skin surface or near-surface dermal layers. While the skin is disinfected with various chemicals, this is typically a relative rather than absolute disinfection, and bacteria will dwell on, or just under, the dead layer of skin cells of the cannulation site. It is known in the field of thoracic surgery to control infection induced by scalpels and the like, by laying over the disinfected skin area intended for surgical cutting a sheet of sterile plastic. This sheet is pressed against the skin, to which it adheres without adhesive. Not only is the outer surface of the sheet a sterile field on which surgical instruments may be placed without contamination, but the sheet's adherence to the skin tends to immobilize bacteria on the skin and under the dead skin cells. Owing to the clarity of the film, it is possible for the surgeon to visualize the cutting area and cut through the film as he/she surgically cuts the patient. Thus, no or few bacteria are dragged into the surgical site during cutting due to the effect of the sterile sheet. Tegaderm is a brand name of this prior art product.
Besides cannulating patients, needles also cannulate injection sites carried on medical devices, such as tube sets, drug vials, IV bags and the like. The prior art injection sites all comprise elastomeric bungs of a hardness not less than about 10 Shore A durometer, and are carried in typically plastic housings that hold the bung fixed and under compressive forces both for sealing the space between the bung and the housing, but also to urge shut the slit caused by a cannulating needle, when removed. Many elastomers are not suitable for injection sites because they either are either cored out when cannulated with a sharp, beveled hollow bore needle, or they leak through the cannulated slit even in the presence of the compressive forces urged on it by the housing. It has not been known until now of a resealable, non-coring elastomeric material that did not require a compressive or retentive rigid housing to be effectively resealable after passage and removal of needles, including hollow bore sharp needles.
Another problem of injection sites is that they must be manufactured into the medical device. For example a dialysis set typically comprises three or more injection sites at various locations on the set. Since many sites are never used during a particular medical procedure, the cost of manufacturing injection sites in every medical device, when only a few are used, represents a great monetary waste. It would be advantageous if a simple, cheap, attachable injection site to medical devices could be developed.